When $4 \ mol$ of $A$ is mixed with $4 \ mol$ of $B$,$2 \ mol$ of $C$ is formed at equilibrium. For the reaction $A + B \rightleftharpoons C + D$,the equilibrium constant is:

Assertion: Reaction quotient is defined in the same way as equilibrium constant at any stage of the reaction.
Reason: If $Q_c < K_c$,the reaction moves in the direction of reactants.

The equilibrium constant for the reaction,$N_2 + 3H_2 \rightleftharpoons 2NH_3$ at $400 \ K$ is $41$. The equilibrium constant for the reaction,$\frac{1}{2} N_2 + \frac{3}{2} H_2 \rightleftharpoons NH_3$ at the same temperature will be closest to

Explain the use of the equilibrium constant to predict the extent of a reaction with an example.

The equilibrium constants for three reactions are given as:
$(I) \, CO_{(g)} + H_2O_{(g)} \rightleftharpoons CO_{2_{(g)}} + H_{2_{(g)}} ; \, k_1$
$(II) \, CH_{4_{(g)}} + H_2O_{(g)} \rightleftharpoons CO_{(g)} + 3H_{2_{(g)}} ; \, k_2$
$(III) \, CH_{4_{(g)}} + 2H_2O_{(g)} \rightleftharpoons CO_{2_{(g)}} + 4H_{2_{(g)}} ; \, k_3$
The correct relationship between their equilibrium constants is:

For the reaction $A + 2B \rightleftharpoons C$,the expression for the equilibrium constant is.........